PRIME Chapter 4 - Gas Turbine

less than Diesel cycle efficiency

Overall efficiency of a gas turbine is __________.

A. equal to Carnot cycle efficiency

B. equal to Rankine cycle efficiency

C. less than Diesel cycle efficiency

D. more than Otto or Diesel cycle efficiency

Simple open cycle gas turbine

Which of the following turbine has least weight per bhp developed?

A. Simple open cycle gas turbine

B. Open cycle gas turbine with inter-cooling and reheating

C. Open cycle gas turbine with inter-cooling reheating and regenerating

D. Closed cycle gas turbine

all of these

Which of the following is/are advantage(s) of closed cycle gas turbine over open cycle gas turbine?

A. no containing of working substance with combustion gases

B. inferior quality fuel can be used

C. low maintenance costs

D. all of the these

5 to 8

The range of compression ratio in a gas turbine is __________.

A. 3 to 5

B. 5 to 8

C. 8 to 12

D. 12 to 20

Atkinson cycle

A constant volume combustion gas turbine operates on __________.

A. Ericson cycle

B. Joule cycle

C. Brayton cycle

D. Atkinson cycle

Unchanged

How does the value for work for unit mass flow of air in the compressor and turbine influenced by the addition of a regenerator?

A. Slightly increased

B. Unchanged

C. Greatly decreased

D. Greatly increased

Brayton cycle

What is the ideal cycle for gas turbine work?

A. Brayton cycle

B. Stag combined cycle

C. Bottom cycle

D. Ericson cycle

Large volume of low pressure air cannot be efficient handled in reciprocating engines

Brayton cycle cannot be used in reciprocating engines even for same adiabatic compression ratio and work output because __________.

A. Brayton cycle is highly efficient

B. Brayton cycle is for low speed engines only

C. Brayton cycle needs large air-fuel ratio

D. Large volume of low pressure air cannot be efficient handled in reciprocating engines

Expansion of gases

In order to increase the gas velocity gas turbines generally have fixed nozzles. This is allow the __________.

A. Compression of gases

B. Condensation of gases

C. Expansion of gases

D. Evaporation of gases

10 MW

Combustion turbines or gas turbines are the preferred combustion engines in application much above _________.

A. 8 MW

B. 9 MW

C. 10 MW

D. 7 MW

In 100 gas to 200 MW range

Large units gas turbine regularly operate __________.

A. In 100 gas to 200 MW range

B. In 50 to 100 MW range

C. Over 150 MW

D. Below 150 MW

30 MW

Small units gas turbine operate below _________.

A. 20 MW

B. 12 MW

C. 30 MW

D. 24 MW

single shaft

Heavy duty gas turbine typically have __________.

A. double shafts

B. single shaft

C. triple shafts

D. quadruple shafts

aeroderivative gas turbine

Which of the following is basically a jet engine that exhausts into a turbine generator?

A. aeroderivative gas turbine

B. industrial gas turbine

C. Brayton engine

D. Joule turbine

40 MW

Most aeroderivative combustion turbine produce less than:

A. 20 MW

B. 30 MW

C. 40 MW

D. 50 MW

11 to 16

The compression ratio based on pressures in the compression stage in a gas turbine is typically __________.

A. 11 to 16

B. 5 to 8

C. 12 to 18

D. 8 to 14

14 to 15

The compression ratio based on pressure of heavy duty gas turbine is in the range of __________.

A. 14 to 15

B. 19 to 21

C. 11 to 16

D. 16 to 18

19 to 21

Aeroderivative combustion turbine have higher compression ratio typically:

A. 14 to 15

B. 19 to 21

C. 11 to 16

D. 16 to 18

1200 C to 1290 C

The temperature of the gas entering the expander section is typically __________.

A. 1200 C to 1290 C

B. 1000 C to 1200 C

C. 1500 C to 1490 C

D. 1300 C to 1390 C

540 C to 590 C

The exhaust temperature which makes the exhaust an ideal heat source for combined cycles is typically:

A. 540 C to 590 C

B. 600 C to 650 C

C. 300 C to 350 C

D. 440 Cto 490 C

3 to 4 expander stages

Most combustion turbines have __________.

A. 2 to 3 expander stages

B. 3 to 4 expander stages

C. 4 to 5 expander stages

D. 1 to 2 expander stages

240 to 250 kg/s

The exhaust flow rate in modern heavy duty turbines per 100 MW is approximately __________.

A. 240 to 250 kg/s

B. 140 to 150 kg/s

C. 340 to 350 kg/s

D. 440 to 450 kg/s

Joule cycle

The Brayton gas turbine cycle is also known as __________.

A. Joule cycle

B. Stirling cycle

C. Ericsson cycle

D. Atkinson cycle

50 to 75 %

Approximately how many percent of the turbine power is used to drive the high efficiency compressor?

A. 50 to 75 %

B. 60 to 85 %

C. 45 to 70 %

D. 30 to 55 %

650 C to 1000 C

Depending on the turbine construction details, the temperature of the air entering the turbine will be between __________.

A. 650 C to 1000 C

B. 750 C to 1100 C

C. 550 C to 950 C

D. 850 C to 1200 C

open combustors

Which of the following engines are typically used by Turbojet and turboprop?

A. open combustors

B. closed combustors

C. turbo combustors

D. high combustors

34 to 36 %

The full load thermal efficiency of existing heavy duty combustion turbines in simple cycle is approximately __________.

A. 34 to 36 %

B. 30 to 32 %

C. 40 to 42 %

D. 26 to 28 %

42 %

Aeroderivative commonly achieve efficiencies up to:

A. 42 %

B. 38 %

C. 45 %

D. 35 %

50 to 75 %

Which of the following is the typically back-work ratio of gas turbine?

A. 50 to 75 %

B. 40 to 65 %

C. 30 to 55 %

D. 35 to 60 %

a cross flow heat exchanger

Which of the following is an example of a generator?

A. a counter flow heat exchanger

B. a cross flow heat exchanger

C. a mixed flow heat exchanger

D. a parallel heat exchanger

less heat is added

Which of the following is an effect of having a regenerator?

A. less heat is added

B. compressor work is reduced

C. turbine work is increased

D. compressor work is increased

compressor and turbine work

A regenerator in a gas turbine has no effect in __________.

A. compressor and turbine work

B. heat added

C. thermal efficiency

D. combustor

increase thermal efficiency

In a Brayton cycle multiple stages of compression and expansion will _________.

A. increase thermal efficiency

B. decrease thermal efficiency

C. limit thermal efficiency

D. control efficiency

increase thermal efficiency

In a Brayton cycle, reheating and intercooling will __________.

A. increase thermal efficiency

B. decrease thermal efficiency

C. limit thermal efficiency

D. control efficiency

heat added

In a Brayton cycle, reheating has no effect in __________.

A. heat added

B. thermal efficiency

C. backwork ratio

D. network

turbine work

In a Brayton cycle, intercooling has no effect __________.

A. turbine work

B. thermal efficiency

C. Back-work ratio

D. network

Wc/Wt

If Wt is the turbine power and Wc is the compressor power then the back-work ratio is __________.

A. Wt/Wc

B. Wc/Wt

C. W𝑡 −W𝑐/W𝑡

D. Wt−W𝑐/W𝑐

2

Physical limitations usually preclude more than how many stages of intercooling and reheating?

A. 2

B. 3

C. 4

D. 5

decrease

For multi-stage compression of an ideal Brayton Cycle, the back work ratio will __________.

A. increase

B. decrease

C. remains the same

D. none of these

11 to 16

In most common designs of Gas turbine, the pressure ratio ranges from __________.

A. 10 to 12

B. 11 to 16

C. 12 to 18

D. 15 to 20

heat is transferred

In Brayton cycle, the __________ during constant pressure process.

A. work is added

B. heat is transferred

C. pressure is rejected

D. energy is added

aircraft propulsion and electric power generation

What are the two major application areas of gas turbine engines?

A. driving automotive engine and locomotives

B. heating and generation

C. aircraft propulsion and electric power generation

D. none of these

10 to 25

Aircraft gas turbines operate at higher pressure ratio typically between __________.

A. 6 to 8

B. 10 to 18

C. 12 to 24

D. 10 to 25

5

The first commercial high-pass ratio engines has a bypass ratio of __________.

A. 1

B. 5

C. 3

D. 7

Decreases

The single-stage expansion process of an ideal Brayton cycle without regeneration is replaced by a multistage expansion process with reheating between the same pressure limits. As a result of modification, what will happen to the thermal efficiency?

A. Increases

B. Remains constant

C. Decreases

D. None of these

All of these

Which of the following is/are the application of Brayton cycle?

A. Propulsion system

B. Automotive Turbine Engines

C. Aircraft Turbine engines

D. All of these

Joule cycle

Brayton cycle is also known as __________.

A. Carnot cycle

B. Diesel cycle

C. Joule cycle

D. Rankine cycle

Brayton cycle

This is applied to propulsion of vehicles because of certain practical characteristics.

A. Diesel cycle

B. Carnot cycle

C. Otto cycle

D. Brayton cycle

5

The first commercial high pass ratio engines has a bypass ratio of __________.

A. 1

B. 5

C. 3

D. 7

increase

In Brayton Cycle, the turbine work will __________.

A. increase

B. remains the same

C. decrease

D. none of these

cycle pressure level

It is the ratio of the maximum pressure in the cycle to the atmospheric pressure.

A. cycle pressure ratio

B. cycle pressure level

C. regenerator effectiveness

D. thermal efficiency

Air rate

The quantity of working medium entering the first stage of compression per unit of output energy.

A. Air rate

B. work ratio

C. thermal efficiency

D. regenerator effectiveness

fuel rate

The quantity of a specified fuel consumed per unit of output energy.

A. air rate

B. fuel rate

C. work ratio

D. thermal efficiency

regenerator effectiveness

It is the ratio of the actual heat transfer in a regenerator to that theoretically possible if the heated fluid could reach the temperature of the entering hot gas.

A. back-work ratio

B. thermal efficiency

C. regenerator effectiveness

D. pressure ratio

work ratio

It is the ratio of output power to the total installed turbine power.

A. work ratio

B. thermal efficiency

C. cycle pressure level

D. regenerator effectiveness

Turbo - prop

Which of the following does not use ambient air for propulsion?

A. Turbo jet

B. Pulse jet

C. Turbo - prop

D. Rocket

increase

Reheating process in Brayton cycle, the turbine work will __________.

A. increase

B. remains the same

C. decrease

D. none of these

two isentropic and two constant pressure processes

Brayton cycle has __________.

A. two isentropic and two constant volume pressure

B. two isentropic and two constant pressure processes

C. one constant pressure, one constant volume , and two adiabatic processes

D. two isothermals, one constant volume and a constant pressure processes

large volume of low pressure air cannot be efficiency handled in reciprocating engines

Brayton cycle cannot be used in reciprocating engines even for same adiabatic compression ratio and work output because __________.

A. Otto cycle is highly efficient

B. Brayton cycle is less efficient

C. Brayton cycle is foe slow speed engines only

D. large volume of low pressure air cannot be efficiency handled in reciprocating engines

Brayton cycle

Which cycle is generally used for gas turbine?

A. Otto cycle

B. Dual cycle

C. Carnot cycle

D. Brayton cycle

A. 1 - 1/𝑟(𝑘−1)/𝑘

When r is the compression ratio, the efficiency of Brayton cycle is given by:

A. 1 - 1/𝑟(𝑘−1)/𝑘

B. 1 - 1/𝑟𝑘−1

C. 1 - 1/𝑟𝑘

D. 1 - 1/r

improves thermal efficiency

A regenerator in a gas turbine __________.

A. reduces heat loss during exhaust

B. allows use of higher compression ratio

C. improves thermal efficiency

D. allows use of fuels of interior quality

axial flow type

Which of the following compressors is generally used for gas turbines?

A. lobe type

B. centrifugal type

C. axial flow type

D. reciprocating type

Brayton cycle

The constant pressure gas turbine works on the principle of ___________.

A. carnot cycle

B. Bell - Coleman cycle

C. Rankine cycle

D. Brayton cycle

open cycle type

What type of gas turbine is used in air craft?

A. open cycle type

B. closed cycle type with reheating

C. closed type with reheating and regeneration

D. open cycle type with reheating, regeneration and intercooling

recover heat from exhaust gases

In a gas turbine combined cycle plant, a waste heat boiler is used to:

A. heat air from intercooler

B. gases from regenerator

C. recover heat from exhaust gases

D. none of the above

Regenerator

The heat exchanger used to provide heat transfer between the exhaust gases and the air prior to its entrance to combustor.

A. Evaporator

B. Combustion chamber

C. Regenerator

D. Heater

16 to 18

Most heavy duty combustion turbines have how many compression stages?

A. 14 to 16

B. 18 to 20

C. 10 to 12

D. 16 to 18

38 to 38.5 %

New combustion turbine on the cutting edge of technology ( Advanced turbine system ) are able to achieve __________.

A. 38 to 38.5 %

B. 36 to 36.5 %

C. 40 to 40.5 %

D. 34 to 34.5 %

Wt − Wc

If W𝑡 is the turbine power and Wc is the compressor power then the network is __________.

A. Wt × Wc

B. Wc / Wt

C. Wt − Wc

D. Wt + Wc

Isobaric process

In Brayton cycle, the heat is transformed during which process?

A. Constant temperature

B. Isobaric process

C. Isentropic process

D. Isochoric process

exit temperature

The use of regenerator is recommended only when the turbine exhaust temperature is higher than the compressor __________.

A. exit temperature

B. mean temperature

C. inlet temperature

D. absolute temperature

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